Botan bindings devlog

I have planned for a SecureMemory class that Botan will provide an implementation of that uses botan_scrub_mem to ensure that memory erasure is not accidentally elided by the compiler. After that, the most important thing will be masking interruptions and squeezing the laziness out to make sure that the IO actions actually fire. Then using it should be no more difficult than supplying a SecureByteStringAllocator instead of a ByteStringAllocator (or putting the appropriate SecureAllocator constraint on the function if you want to force it)